refactor: address Copilot review on /scripts/:script_hash/utxos
- Import `Amount` as a type-only import (used only as a type). - Type `reference_script_hash` as non-null: the query inner-joins `script` and filters on its hash, so the column is always present. - Simplify the `amount` array construction using the `...(row.amount ?? [])` pattern already used by /accounts/:stake_address/utxos. Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>